The present invention relates to a charging system for recharging a battery in an automobile and, more particularly, to a system for regulating a charge voltage delivered to a battery in an automobile.
An automobile battery is an electrochemical device that produces and stores electricity. Typically, an automobile battery is a xe2x80x9c12-voltxe2x80x9d direct-current (DC) battery which actually produces approximately 12.6 volts of electricity. Such a 12-volt battery generally includes a series of six elements or cells wherein each cell produces approximately 2.1 volts. Each cell generally includes a container wherein a positive plate and a negative plate are situated separate from each other and covered within a bath of electrolyte. The electrolyte, often referred to as xe2x80x9cbattery acid,xe2x80x9d is generally a mixture of distilled water and sulfuric acid.
When a driver inserts and turns a key in the ignition of an automobile, the electric starting motor of the automobile starting system draws electrical power (electric current) from the battery and converts that electrical power into mechanical power to crank and start up the engine. In doing so, the battery is discharged (electrically weakened) to some degree due to the electric current flow out of the battery. As a result, the battery must at some time be recharged to ensure that the automobile can be successfully started up again in the future.
To recharge the battery, the automobile includes a charging system. The charging system in a modern automobile typically includes (1) a generator (also known as an alternator), (2) a generator drive belt, (3) a voltage regulator, (4) a charge indicator, and (5) a charging system harness. The generator is a DC (direct current) generator that converts mechanical power from the engine into electrical power such as an electric voltage and current. This electrical power is communicated from an output terminal of the generator to the battery to thereby recharge the battery. The generator drive belt, on the other hand, serves to couple the crankshaft pulley on the engine to a drive pulley on the generator, thereby transferring mechanical power from the engine to the generator. Further, the voltage regulator, a very important and key element in the charging system of an automobile, is an electrical device that dictates, controls, and regulates the levels of the output voltage and current produced by the generator for recharging the battery. In addition, the charge indicator is generally a visual indicator which visually communicates to a driver the operational health of the charging system and/or the battery. The charge indicator may include, for example, a warning light, with or without a voltmeter indicator or an ammeter indicator, visibly situated in the dash, instrument panel, or driver information center (DIC) of the automobile. Lastly, the charging system harness is a wire harness that contains the many wires that are electrically interconnected between the various parts and elements of the charging system.
Once the engine is started up with the starting system and successfully running, the charging system then takes over to provide electric current to the battery as well as provide electric current to the electrical systems and many various electrical loads associated therewith within the automobile. More particularly, when the engine is started up and running, the spinning crankshaft pulley on the engine then motivates the generator drive belt to mechanically spin the drive pulley on the generator. In this way, the generator is able to use the mechanical action of the drive pulley to generate and produce an electric current at the generator output terminal. This electric current produced and output by the generator is utilized to both recharge the battery and operate the electrical systems and various electrical loads associated therewith within the automobile when the engine is running. Some of the various electrical loads may include, for example, front and rear HVAC (heating, ventilation, and air-conditioning) blowers, an AC (air-conditioning) compressor clutch, front and rear heated seats, heated mirrors, a rear window defogger, a rear window wiper, courtesy door lights, interior lights, engine cooling fans, etc.
While the engine is running, the voltage regulator of the charging system works to both generally maintain and vary the output voltage of the generator within a predetermined optimum voltage range, such as, for example, 13 to 16 volts. By maintaining the generator output voltage within such a voltage range, electric current from the generator is, first of all, thereby driven into the battery to successfully recharge the battery since the voltage range is higher than the inherent voltage level (12.6 volts) of the battery. In addition, maintaining the generator output voltage within such a range also enables the generator to simultaneously supply electric current and voltage power to the many different electrical systems and various electrical loads within the automobile for their proper operation as well. Furthermore, by working to maintain the generator output voltage within an optimum voltage range in this way, the voltage regulator also thereby prevents the problems commonly associated with undercharging or overcharging the battery. For example, if the battery is undercharged, then the likelihood that the battery will not be able to successfully crank and start up the automobile again in the future is undesirably increased. On the other hand, if the battery is overcharged, then the battery may overheat or experience xe2x80x9cgassingxe2x80x9d (the formation of acid fumes within the battery) and become permanently damaged.
In addition to merely maintaining the generator output voltage within an optimum voltage range, an ideal voltage regulator must also precisely vary the generator output voltage within the optimum voltage range to accommodate abrupt changes in operating conditions concerning the battery, the engine, and the various electrical loads within the automobile. In doing so, the voltage regulator thereby attempts to both conserve battery life and improve the overall fuel economy of the automobile. For example, with regard to the battery, to ensure that the battery is fully recharged while the engine is running and before the ignition and engine are turned off, an ideal voltage regulator will dictate that the generator produce an output voltage near the high end of the optimum voltage range when the engine is initially started up and running. In this way, if the engine is only turned on for a brief period of time, for example, when the automobile is used for a very brief trip, the battery is successfully recharged before the engine is turned off. Once, however, the battery is fully recharged while the engine is running, the voltage regulator will reduce the generator output voltage so that the output voltage settles at or near the low end of the optimum voltage range. In doing so, the voltage regulator helps prevent overcharging and gassing, preserve battery life, preserve the lives of headlights and other various lights, within the automobile, and improve the overall fuel economy of the automobile. As another example, if the automobile is idling in extremely slow traffic with numerous electrical loads activated and thereby heavily discharging the battery, an ideal voltage regulator will quickly dictate that the generator output voltage be set near the upper end of the optimum voltage range once the automobile breaks free from traffic and travels at a higher rate of speed on the open road to ensure that the battery is fully recharged before the engine is turned off. Once the battery is fully recharged in this way, the voltage regulator will then dictate that the generator output voltage be reduced and settle back down at or near the lower end of the optimum voltage range. As these examples illustrate, an ideal voltage regulator should timely and precisely dictate the output voltage of the generator to prevent the battery from being undercharged, wherein the battery will not be able to restart the car in the future, and to prevent the battery from being overcharged, wherein undesired overheating or gassing of the battery will occur. Again, in doing so, the voltage regulator thereby helps preserve battery life, as well as the life of various lamps (i.e., lights) and other electrical components within the automobile, and helps improve the overall fuel economy of the automobile. Although the voltage regulators within many modern automobiles attempt with some measure of success in achieving some of these goals, there is yet to date much room for needed improvement.
For the voltage regulator to be able to timely and precisely adjust and dictate the output voltage of the generator to successfully recharge and maintain the battery at a proper charge level at all times, an ideal voltage regulator must, on an ongoing periodic basis, obtain and consider up to date information regarding both (1) the everchanging temperature of the battery and (2) the everchanging xe2x80x9cstate of chargexe2x80x9d (SOC) of the battery. For example, with regard to temperature, if the temperature of the electrolyte within the battery (hereinafter the xe2x80x9cbattery temperaturexe2x80x9d) is very low due to cold weather, the chemical action of the battery is slowed such that the battery requires a higher voltage to be recharged than it would have required had the battery temperature been higher. In such a case, the voltage regulator must estimate the battery temperature so that the voltage regulator may, for an appropriate period of time, determine and dictate an appropriate generator output voltage at or near the upper end of the optimum voltage range which will sufficiently charge the battery and/or operate the electrical systems and thereby overcome the adverse effect of the cold temperature. In contrast, if the battery temperature is very high, the chemical action of the electrolyte within the battery is no longer slowed. In such a case, the voltage regulator must estimate the battery temperature and recognize the situation as such so that an appropriate generator output voltage can be determined and dictated that will successfully recharge the battery and/or operate the electrical systems without causing overheating or gassing within the battery. On the other hand, with regard to the state of charge of the battery, if the state of charge of the battery is low (that is, the battery is electrically weak due to discharging), then the voltage regulator must estimate the state of charge of the battery to determine the extent and particular degree of the battery""s weakened condition. In doing so, the voltage regulator can then precisely adjust the output voltage of the generator upward and thereby successfully recharge the battery to a proper charge level and/or operate the electrical systems without undercharging or overcharging the battery. In contrast, if the state of charge of the battery is high, then the voltage regulator must estimate the state of charge of the battery to recognize the situation as such so that an appropriate generator output voltage can be determined and dictated that will successfully recharge the battery and/or operate the electrical systems without undercharging or overcharging the battery.
In known prior art charging systems, the voltage regulators included therein often utilize a temperature sensor, such as a thermistor, which is situated on or proximate the battery (for example, within the battery tray) and connected to a xe2x80x9csensexe2x80x9d or xe2x80x9csensingxe2x80x9d terminal (often referred to as an S-terminal) of the generator with one or more wires to periodically estimate the temperature of the battery. In addition, such voltage regulators also often utilize an integrated circuit (IC) which is installed at the battery and connected to the voltage regulator with one or more wires to periodically sense the current state of charge of the battery. In such a configuration, the voltage regulators of such known prior art charging systems gather information about both the temperature of the battery and the state of charge of the battery in an attempt to timely and precisely adjust the output voltage of the generator to help ensure that the battery is properly charged. However, using such means for periodically monitoring both the temperature and state of charge of the battery are typically very expensive, for such requires a significant amount of extra wiring and additional electronic components.
Thus, in light of the above, there is a present need in the art for a method and/or system for regulating a charge voltage delivered from a generator and to a battery which (1) successfully and accurately monitors both the temperature and the state of charge of the battery, (2) timely and precisely adjusts the generator output voltage to prevent undercharging and overcharging as well as gassing in the battery, (3) improves battery life, the life of various lights within the automobile, and overall automobile fuel economy, and (4) accomplishes (1), (2), and (3) with a minimal amount of wiring and electronic components to thereby reduce production costs.
The present invention provides a method of regulating a charge voltage delivered to a battery in an automobile that has an engine and an ignition system capable of being activated with an ignition switch. The method successfully extends the life of the battery and also helps improve the overall fuel economy of the automobile. According to the present invention, the method basically includes, first of all, the steps of periodically estimating the electrolyte temperature of the battery when the ignition switch is on, periodically sensing the voltage of the battery when the ignition switch is on, and using the estimated electrolyte temperature and the sensed voltage to estimate the electric current of the battery. In addition, the method also basically includes the steps of using the estimated electric current to estimate the amp-hours into the battery, using the estimated amp-hours to estimate the state of charge of the battery when the engine is running, and using the running state of charge and the estimated electrolyte temperature to determine an optimum charge voltage for the battery. Furthermore, the method also basically includes the steps of using the sensed voltage to adjust the optimum charge voltage, communicating the optimum charge voltage to a generator, and using the generator to deliver a charge voltage to the battery wherein the charge voltage is regulated by the optimum charge voltage.
In a preferred methodology of the present invention, the method also includes the steps of periodically sensing the open-circuit voltage of the battery when the ignition switch is off, using the sensed open-circuit voltage and the estimated electrolyte temperature to estimate the state of charge of the battery when the ignition switch is initially turned on for starting up the engine, and also using the estimated start-up state of charge to estimate the state of charge of the battery when the engine is running. In a highly preferred methodology of the present invention, the method also includes the step of determining the length of time that the ignition switch was off when the ignition switch is initially turned on and the step of using the sensed open-circuit voltage and the estimated electrolyte temperature to estimate the start-up state of charge of the battery only when the length of time that the ignition switch was off is greater than a predetermined rest time for the battery. The predetermined rest time for the battery is preferably selected from a range of only a couple of hours to several hours.
Also, in a preferred methodology of the present invention, the basic step of periodically estimating the electrolyte temperature of the battery when the ignition switch is on preferably includes the step of sensing the temperature of the air entering into the engine. Sensing the temperature of the air entering into the engine is preferably accomplished with an intake air temperature sensor situated on the engine.
Further, in a preferred methodology of the present invention, the method also includes the step of using the running state of charge and the estimated amp-hours to determine an appropriate boost level of the idle speed of the engine. In addition, the method also preferably includes the step of using the running state of charge and the estimated amp-hours to determine an appropriate reduction or shed level of various electrical loads on the vehicle. Such various electrical loads may include, for example, front and rear HVAC blowers, an air-conditioning compressor clutch, front and rear heated seats, heated mirrors, a rear window defogger, a rear window wiper, door lights, interior lights, engine cooling fans, etc.
To implement the method described hereinabove, the present invention also provides a system for regulating a charge voltage delivered to a battery in an automobile having an engine. According to the present invention, the system basically includes, first of all, a generator and an engine control module. The generator has an output terminal capable of being electrically connected to the battery for delivering a charge voltage to the battery. The engine control module is electrically connected to the generator and is capable of sensing an electric feedback signal from the generator. In addition, the system also basically includes a sensor capable of sensing the temperature of the air entering into the engine, an actuator capable of adjusting the idle speed of the engine, and a data link. The air temperature sensor, the idle speed actuator, and the data link are all electrically connected to the engine control module. Furthermore, the system also basically includes a body control module electrically connected to the data link, a plurality of body controllers also electrically connected to the data link, and a plurality of electrical loads electrically connected to the body controllers. The body control module is capable of being electrically connected to the battery and has means for sensing the voltage of the battery. The electrical loads are capable of being powered by the generator and/or the battery. In such a configuration, the body control module is capable of using the sensed electric feedback signal, the sensed air temperature, and the sensed battery voltage to determine an optimum charge voltage for the battery, adjust the idle speed of the engine, and selectively reduce or shed the electrical loads. The engine control module is capable of communicating the optimum charge voltage to the generator such that the generator is capable of delivering a charge voltage to the battery which is regulated by the optimum charge voltage.
In a preferred embodiment of the present invention, the system also includes a driver information center (DIC) electrically connected to the data link. The DIC serves to visually and/or audibly convey operational information concerning the automobile to a human driver. Furthermore, the system also preferably includes a data link connector electrically connected to the data link. The data link connector provides electrical access to information on the data link so that diagnostic testing can be performed by a technician.
Advantages, design considerations, and applications of the present invention will become apparent to those skilled in the art when the detailed description of the best mode contemplated for practicing the invention, as set forth hereinbelow, is read in conjunction with the following drawings.